Cache Backup Device in Write-Protect Mode

What Caused the Problem?

A cache backup device is currently in write-protect (read-only) mode. While in write-protect mode, cached data cannot be written to the backup device. The Recovery Guru Details area provides specific information you will need as you follow the recovery steps.

Caution: Electrostatic charges can damage sensitive components. Always use proper antistatic protection when handling components. Touching components without using a proper ground may damage the equipment.

Important Notes

The purpose of a cache backup device is to preserve cached data in the event of a power failure. Therefore, you should resolve this problem as soon as possible.
If there is also an "Insufficient Cache Backup Device Capacity" problem displayed in the Summary area, read the following additional important notes:
- The "Insufficient Cache Backup Device Capacity" problem is most likely a direct result of the cache backup device in write-protect mode. The writable cache backup device capacity is now less than the amount of the RAID controller module's cache, and therefore, cannot back up the cached data in the event of a power failure.
- Complete the Recovery Steps for this problem (Cache Backup Device in Write-Protect Mode) first.
- Write caching for all virtual disks has been automatically suspended. Write caching will be reinstated after the RAID controller module has been replaced (see the Recovery Steps below).
The RAID controller module servicing procedure varies depending on whether your storage array has one or two RAID controller modules. Consult the appropriate hardware manual if you need details on locating and replacing the RAID controller modules.

Recovery Steps

If...	Then...
Your storage array has one RAID controller module	Go to "Procedure for Storage Arrays with One RAID Controller Module."
Your storage array has two RAID controller modules	Go to "Procedure for Storage Arrays with Two RAID Controller Modules."

Procedure for Storage Arrays with One RAID Controller Module

Stop all I/O from all hosts to this storage array. When the Cache Active LED on the RAID controller module is no longer blinking (may take several minutes), proceed to step 2.

Caution: Risk of Data Loss. You must wait for the Cache Active LED to stop blinking to ensure that all cache has been written to disk.

Click the Save As button in the Recovery Guru dialog to save the remaining steps to file. The remaining Recovery Steps will no longer be accessible from the Recovery Guru dialog after you complete step 3.

Remove the RAID controller module module that contains the affected cache backup device (listed in the Component requiring service field in the Details area).

Refer to the Summary tab to view which management method you are using to manage this storage array.

If...

Then...

You are using In-Band management for ALL hosts attached to this storage array

Go to step 5.

You are using Out-of-Band management for ANY host attached to this storage array

Before you insert a new RAID controller module module into the storage array, you must update the DHCP/BOOTP server so that it will associate the new RAID controller module's hardware Ethernet (MAC) address with the DNS/network name and IP address previously assigned to the removed RAID controller module.

To update the DHCP/BOOTP server, find the entry associated with the removed RAID controller module and replace its Ethernet (MAC) address with the new RAID controller module's Ethernet (MAC) address. The RAID controller module's Ethernet (MAC) address is located on an Ethernet ID label on the RAID controller module module in the form xx.xx.xx.xx.xx.xx.

When you are finished, go to step 5.

If the new RAID controller module module does NOT contain a battery, insert the battery from the old RAID controller module module into the new replacement RAID controller module module. Consult your hardware documentation for details.

Insert the RAID controller module module securely into place.

Note: Write caching will be reinstated (if applicable for each virtual disk) once the RAID controller module's battery is fully charged and has completed any required learn cycles (if applicable).

Click the Recheck button to rerun the Recovery Guru. The failure should no longer appear in the Summary area. If the failure appears again, contact your technical support representative.

Procedure for Storage Arrays with Two RAID Controller Modules

If there are any hosts connected to this storage array that are NOT running a host-based, multi-path failover driver, stop I/O to the storage array from each of these hosts.

Place the affected RAID controller module offline. The affected RAID controller module is listed in the Component requiring service field in the Details area.

a	From the Support tab, click the Manage RAID Controller Modules link, and then click the Place RAID Controller Module Online of Offline link.
b	Select the affected RAID controller module, then select Place RAID controller module offline.
c	Click the OK button.

Read all of the following steps before taking any action. The remaining Recovery Steps will no longer be accessible from the Recovery Guru dialog after you complete step a.

a	Click the Recheck button to rerun the Recovery Guru.
b	Select the "Offline RAID Controller Module" problem that is being reported in the Summary area.
c	Complete the Recovery Steps in the "Offline RAID Controller Module" recovery procedure to replace the affected RAID controller module.

Note: Additional information on this issue may be available. Please visit the Dell support website at support.dell.com and select your product model. Choose "troubleshooting" as your tool option, then search by this procedure title.